Cellular myofibromas with SRF fusions: clinicopathological and molecular study of 3 cases of a rare entity and a potential mimic of sarcoma.

Cellular myofibromas/myopericytomas harboring recurring SRF fusions are recently characterized as rare and diagnostically challenging entities, which can mimic myogenic sarcomas. These tumors belong to the pericytic/perivascular myoid tumor family, which comprises a group of genetically heterogenous and sometimes morphologically overlapping entities. In this series, we describe 3 cases of SRF-rearranged cellular myofibromas/perivascular myoid tumors with a smooth muscle-like phenotype in children. The children ranged from 7 to 16 years of age, and all presented with a painless mass in the extremities, 2 of which were deep-seated. Histologically, the tumors demonstrated a smooth muscle-like morphology and immunophenotype with mild atypia and low-level mitotic activity. Prominent dense collagen deposition and coarse calcification was observed in 2 tumors. RNA sequencing revealed SRF fusions in all cases, with each tumor showing a different 3' partner gene, RELA, NFKBIE, and NCOA3. Of these, NCOA3 has not been reported previously, and this expands the molecular spectrum by identifying a novel fusion partner for SRF. Given that histological features can be worrisome for a myogenic sarcoma, wider awareness of this emerging tumor is valuable to avoid potential misclassification.

Surfactin secreted by Bacillus amyloliquefaciens Ba01 is required to combat Streptomyces scabies causing potato common scab.

Potato common scab, which is mainly caused by the bacterium Streptomyces scabies, occurs in key potato growing regions worldwide. It causes necrotic or corky symptoms on potato tubers and decreases the economic value of potato. At present, there is no recommended chemical or biological control for combating potato common scab in Taiwan. It can only reduce the occurrence by cultivation control, but the efficacy is limited. Previously we found that Bacillus amyloliquefaciens Ba01 could control potato common scab in pot assay and in the field. The potential anti-S. scabies mechanism was associated with surfactin secretion, but further molecular dissection was not conducted. Thus, in this study we aimed to determine whether surfactin is the main compound active against S. scabies by knocking out the srf gene cluster in Ba01. The cloning plasmid pRY1 was transformed to Ba01 by electroporation for in-frame deletion. Two independent Δsrf mutants were obtained and confirmed by specific primers and mass spectrometry. The swarming ability and S. scabies inhibition was significantly decreased (P<0.001) in Δsrf mutants. The swarming ability of Δsrf mutants could be restored by the addition of surfactin. Furthermore, we found that Ba01 formed wrinkled biofilm in MSgg liquid medium, while Δsrf mutants formed biofilm abnormally. Furthermore, the α-amylase, protease and phosphate-solubilizing ability of Δsrf mutants was decreased, and the mutants could not inhibit the growth and sporulation of S. scabies on potato tuber slices. In conclusion, srf gene cluster of B. amyloliquefaciens Ba01 is responsible for the secretion of surfactin and inhibition of S. scabies.